JP3896133B2 - Induction heating apparatus and image forming apparatus including the same - Google Patents

Description

  The present invention includes a fixing device in a dry electrophotographic device, a drying device in a wet electrophotographic device, a drying device in an ink jet printer, a heating device using an induction heating method that is preferably implemented in an erasing device for rewritable media, and the like. The present invention relates to an image forming apparatus.

In a roller-type heating device, for example, in a fixing device used in an electrophotographic copying machine or printer, a configuration in which a halogen lamp is provided in the heating roller and the heating roller is heated by the halogen lamp has been conventionally used. Widely used. However, there is a problem that the rise at the start of heating is slow, and in recent years, a heating roller is formed with a conductive layer, and by applying an alternating magnetic field from the magnetic field generating means provided in the heating roller to the heating roller, Attention has been focused on an induction heating type fixing device in which the heating roller itself is heated using Joule heat generated by an eddy current generated in the heating roller.
Such an induction heating type fixing device is described in Patent Document 1, for example.

  The roller induction heating device as described above is more efficient than the heating device using the halogen lamp because the heating roller itself generates heat. However, in order to heat more efficiently, the skin effect is added. It is necessary to reduce the heat capacity of the heating roller, for example, to make it thin. For this reason, the heat retaining property of the heating roller is lowered and it becomes easy to cool. When reheating is performed after the heating is stopped, there is a problem that it takes time until the temperature is set again to the specified temperature and the response is poor.

  Further, the fixing device disclosed in Patent Document 1 is basically composed of a roller pair composed of a heat roller 201 and a pressure roller 202 as shown in FIG. 16, and the heat roller 201 is disposed on the outer periphery of the roller. The temperature is raised to a predetermined temperature by receiving an alternating magnetic field generated by the induction heating body 207 including the arranged heating coil 209 and insulating support 208.

  On the other hand, a sheet 222 having an unfixed image sent to a fixing unit through a developing process (not shown) is a contact nip formed by a heat roller 201 and a pressure roller 202 that are heated to a predetermined temperature. Pass through. At this time, the unfixed image on the paper 222 is fixed on the paper 222 by heat and pressure.

  As described above, in the fixing device having a standard configuration including the heat roller 201 and the pressure roller 202, when the induction heating body 207 for heating the heat roller 201 is disposed outside the heat roller 201, the heating coil 209 is supplied. Since most of the electric power is used to increase the temperature of the heat roller 201, in addition to the feature of the induction heating method in which the heating efficiency is increased, the assembly work of the heat roller 201 can be simplified and the heat roller 201 can be reduced in diameter. It is described that the fixing device and the laser printer can be miniaturized.

However, the conventional fixing device has the following problems.
(1) Since the heating coil (induction coil) generates Joule heat by the action of a current flowing through the heating coil, the temperature of the coil rises with energization. For this reason, when the heating coil is integrally formed on the insulating support (insulating member), there is a problem that the two are separated from each other due to the difference in thermal expansion during repeated operation (because the difference in linear expansion coefficient is large).

  (2) When the heating coil portion is directly molded on the insulating support, the temperature from the heat roller (heating member) is transmitted in the form of direct heat conduction through the insulating support, so the temperature of the heating coil rises. However, since the resistance component is increased, the efficiency is lowered.

  (3) The heating efficiency is not yet sufficient, and there is a loss. Therefore, in order to improve the heating efficiency, it has been necessary to take measures such as increasing the number of turns of the coil and arranging the heating coil close to the heat roller (heating member).

  However, an increase in the number of turns of the coil causes an increase in the length of the wire element constituting the heating coil, so that the resistance component increases. If the heating coil is disposed close to the heat roller, the temperature of the heating coil is reduced by the heat. Since the resistance component increases due to an increase due to the influence of heat from the roller, both increase the loss due to Joule heat in the heating coil, so there is a limit.

Japanese Patent No. 2616433

  An object of the present invention is to provide an induction heating device that suppresses temperature fluctuation, has a fast warm-up, is excellent in thermal efficiency, is low in cost, is high in safety and reliability, and an image forming apparatus including the induction heating device.

The present invention comprises a heating member having a conductive layer in which current is induced in a varying magnetic field;
A magnetic field generating means arranged to surround the heating member and for generating a variable magnetic field in the conductive layer;
An induction heating device that is disposed opposite to the heating member and includes a pressure member that presses the heated material against the heated member in order to transmit the heat of the heated member to the heated material,
A magnetic member is provided along the outer periphery of the magnetic field generating means,
Either the cross-sectional area of the magnetic member perpendicular to the longitudinal direction of the heating member, the length along the circumferential direction of the heating member, or the distance to the magnetic field generating means varies along the longitudinal direction of the heating member. and,
An insulating member disposed between the magnetic field generating means and the heating member, and formed separately from the magnetic field generating means;
An induction heating apparatus characterized in that a low-permeability good heat conductive member is provided on at least one surface of the insulating member on the heating member side or the magnetic field generating means side .

According to the present invention, by disposing the magnetic member on the back side of the magnetic field generator hand stages (heating member opposite), among the fluctuating magnetic field generated by the magnetic field generating means, it is possible to concentrate the magnetic flux on the rear side it can. When the magnetic flux on the back side is concentrated, the magnetic flux density linked to the heating member on the opposite side is also increased due to the influence . When pressure heat member interlinked magnetic flux density increases, the eddy current generated in the heating member is increased, the calorific value increases. For the above reasons, if a magnetic member is disposed on the back side of the magnetic field generating means , the amount of heat generated by the heating member increases, so that the heating efficiency is improved.

Further, since the magnetic field generating means is disposed outside of the heating member has a curvature, there is an effect that magnetic flux concentration effect is greater to the heating member, be concentrated effectively flux in the magnetic member of small amounts it can.

Further, the magnetic member, so it becomes possible to concentrate the magnetic flux efficiently to the heating member, it is possible to widen the distance between the heating member and the magnetic field generating means. That is, the influence of the temperature of the heating member can be made less susceptible. Thus, the resistance of the magnetic field generating means is lowered since it is possible to lower the temperature of the atmosphere of the magnetic field generating means, can be improved heating efficiency Joule loss is reduced.

Furthermore, the magnetic flux distribution linked to the heating member can be controlled by changing the cross-sectional area / length of the magnetic member or the distance from the magnetic field generating means according to the location of the magnetic member. Thus, the heating value of the both end portions thermal partial relief often such a heating member, without changing the winding pitch and the like of that when a magnetic field generating means or for example induction coils, it is possible to easily increase the temperature The distribution can be made uniform.

  The magnetic member may be divided and arranged, or the same effect may be obtained by changing the relative magnetic permeability of each. The magnetic member may be supported by an insulating member.

In addition , by constituting the magnetic field generating means and the insulating member separately, it is possible to prevent peeling failure due to the difference in thermal expansion coefficient between them. Also, the insulating member may be arranged holder (holding) portion for holding the magnetic field generating hand stage.
Furthermore, by providing a good heat conductive member in part of the insulating member, the temperature distribution in the longitudinal direction of the insulating member can be made uniform. Thereby, the twist, the deflection | deviation, etc. by the temperature nonuniformity of an insulating member can be prevented.
In addition, since the distribution of the heat flux in the longitudinal direction of the heating member that reaches the magnetic field generation means from the heating member through the insulating member can be made uniform, the temperature around the magnetic field generation means does not change extremely depending on the location. The life of the magnetic field generating means is prolonged.
Further, the heat conductive member may be configured to reach the outside of the heating member, and the heat rise around the magnetic field generating means may be suppressed by releasing the heat from the heating member to the outside.
When the heat-conductive member is on the side facing the heating member, the surface treatment may be performed so that the surface has a low emissivity.

In the invention, it is preferable that the insulating member is made of a heat insulating material.
According to the present invention, the insulating member, prevents the temperature rise of the magnetic field generating hand Danshu circumference that occur in the heat of the heating element is transmitted, it is possible to suppress increase in resistance due to temperature rise of the magnetic field generating means.

In addition, the present invention is an image forming apparatus including the induction heating device.
According to the present invention, an image forming apparatus that achieves the above-described excellent effects can be obtained.

According to the present invention, the magnetic field generating hand stage, placed in pressurized thermal unit Zaigai section, by disposing the magnetic member on the back side of the magnetic field generator hand stages (heating member opposite), the heating member side Since the magnetic flux can be concentrated on the substrate, the heating efficiency can be improved. Further, since the magnetic member concentrates the magnetic flux, the distance between the heating member and the magnetic field generating means can be increased, and the temperature effect of the heating member can be made less susceptible to improve the heating efficiency. .

Furthermore, the magnetic flux distribution linked to the heating member can be controlled by changing the cross-sectional area / length of the magnetic member or the distance from the magnetic field generating means according to the location of the magnetic member, the heating value of the heat portion escape many of the heating member, without changing the winding pitch and the like of that when the magnetic field generating means is an inductive coil for example, and easily increases, it can be made uniform temperature distribution .

By the or magnetic field generating means and the insulating member separately configured, it is possible to prevent peeling destruction both by the difference in thermal expansion coefficient.
Further, by providing a good heat conductive member in a part of the insulating member, the temperature distribution in the longitudinal direction of the insulating member can be made uniform, and twisting, deflection, etc. due to temperature unevenness of the insulating member can be prevented. In addition, since the distribution of the heat flux in the longitudinal direction of the heating member that reaches the magnetic field generation means from the heating member through the insulating member can be made uniform, the temperature around the magnetic field generation means does not change extremely depending on the location. The life of the magnetic field generating hand is prolonged.

According to the invention, by a material having a heat insulating property of the insulating member, the insulating member, prevents the temperature rise of the magnetic field generating hand Danshu circumference that occur in the heat of the heating element is transmitted, the magnetic field The increase in resistance due to the temperature rise of the generating means can be suppressed.

According to or present invention, it is possible to obtain an image forming apparatus to achieve the excellent effects described above.

FIG. 1 is a cross-sectional view in the direction perpendicular to the axis of a fixing device 101 in a dry electrophotographic apparatus, which is an induction heating apparatus of a first reference embodiment that serves as a reference for explaining the present invention, and FIG. FIG. 3 is a cross-sectional view of the fixing device 101 in the axial direction. The fixing device 101 generally includes a heating roller (heating member) 102, a pressure roller (pressure member) 103, a magnetic field generation member (magnetic field generation means) 104, and a heat storage member 105. The heating roller 102 has a hollow structure and heats the material to be heated. The pressure roller 103 is disposed to face the heating roller 102 and is urged in a direction to press the heating roller 102 by an elastic member (not shown). The magnetic field generating member 104 is disposed so as to surround the heating roller 102. The heat storage member 105 is disposed in the heating roller 102 via an air layer.

  The fixing device 101 having such a configuration heats the toner transferred to the recording paper 106 by sandwiching and conveying the sheet-like recording paper 106 as a material to be heated between the heating roller 102 and the pressure roller 103. It is melted and fixed on the recording paper 106. In FIG. 1, the toner 107 before fixing is changed to the toner 108 after fixing.

  The heating roller 102 includes at least one conductive layer 109 that generates heat in an alternating magnetic field, and a hollow cylindrical body formed by covering the outer peripheral surface of the heating roller 102 with a release layer 110. It is configured to be rotatably supported by. The conductive layer 109 is a calorific value per magnetic flux, such as metal materials such as nickel and chromium, and ferritic alloy materials such as Si-Fe alloys (silicon steel), Al-Fe alloys, Ni-Fe alloys, and Co-Fe alloys. Made of large material. The release layer 110 is made of a material having good releasability of a welding toner such as silicone rubber and a fluororesin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene). Become. The heating roller 102 is formed with an outer diameter of 30 mm and an inner diameter of 28 mm, for example, and the release layer 110 is formed with a thickness of 50 μm, for example, so that the conductive layer 109 and the magnetic field generating member 104 are close to each other.

  The pressure roller 103 is formed by providing an elastic layer made of silicone rubber having a thickness of 7.5 mm on an aluminum core having a diameter of 15 mm, for example. The pressure roller 103 is pressed against the heating roller 102 with an elastic member such as a spring, for example, with a load of 100N. As a result, a fixing nip portion Y (fixing nip width 3.5 mm) is formed. Further, the heating roller 102 is configured to be rotated by a driving unit (not shown), and the pressure roller 103 is rotated by the rotation of the heating roller 102.

  The heat storage member 105 may be a member having a large heat capacity, and is made of, for example, a metal such as aluminum or iron, or a heat resistant resin such as PPS (polyphenyl sulfide) or PI (polyimide). In particular, by being composed of iron, it is heated by the leakage magnetic flux, so the heat storage effect can be further increased. The heat storage member 105 formed in a cylindrical shape has a heat insulating member 112 composed of a large-diameter plate-like portion 112a fitted into both end portions thereof and a small-diameter shaft portion 112b rotatably supported on the machine body side. Thus, while being rotatably supported by the airframe (not shown), the inside thereof is hermetically sealed.

  The heat insulating member 112 is made of a general heat resistant resin such as PPS, PI, or fluororesin. The inside of the heat storage member 105 is hollow in FIGS. 1, 2 </ b> A, and 2 </ b> B, but may be solid. In the case of a hollow, the inside may be an air layer, or a liquid or the like may be enclosed. Furthermore, in FIG. 2A, the heat storage member 105 and the heat insulating member 112 are formed as separate members, but as is clear from FIG. 2A, the cross-sectional area in the direction perpendicular to the axis is the heat storage member 105. When the heat conduction to the machine body side can be controlled differently on the side (large-diameter plate-like portion 112a) and the heat insulating member 112 side (small-diameter shaft portion 112b), the same material may be used. Moreover, as shown in FIG.2 (b), you may comprise the slit 117 which makes the cross-sectional area by the side of the heat insulation member 112 still smaller.

  For example, as shown in FIG. 3 (a), the magnetic field generating member 104 has a structure in which a solid wire having an insulating coating (for example, a resin / oxide film) applied to its surface is wound with an air core. Things are used. Alternatively, as shown in FIG. 3B, it has a core 114 made of permalloy, sendust, mu metal, pure iron, silicon steel, etc., and made of a heat-resistant resin such as PPS (polyphenyl sulfide), PI (polyimide). A bobbin 115 formed by winding a coil 116 may be used. The magnetic field generating member 104 is connected to the excitation circuit 118. A temperature detecting element 113 made of a thermistor or the like is in contact with the outer peripheral surface of the heating roller 102 in the vicinity of the nip portion Y. In response to the detection result and an image formation request, the magnetic field generating member 104 is fed with a high-frequency current. Is applied and controlled to a predetermined temperature.

  The magnetic field generating member 104 is disposed so as to surround the heating roller 102 except for the nip portion Y. Therefore, as compared with the configuration in which the induction coil (magnetic field generating member 104) is disposed in the heating roller 102, the magnetic flux passing through the heating roller 102 per unit current can be increased, which is highly efficient and easy to assemble. Thus, the degree of freedom in manufacturing and design can be improved, for example, the roller diameter can be reduced.

  Next, the operation of the fixing device 101 configured as described above will be described. First, at the time of warm-up, the excitation circuit 118 is turned on, the induction coil is excited, an alternating eddy current is induced in the conductive layer 109 of the heating roller 102, and heat is generated by Joule heat. The amount of heat generated at this time is 800 W, for example. At the same time as energization by the excitation circuit 118 starts, the pressure roller 103 is driven to rotate as the heating roller 102 is driven to rotate. The surface temperature of the heating roller 2 is always detected by the temperature detecting element 113. When the surface temperature of the heating roller 102 reaches a specified temperature (for example, 180 ° C.), the warm-up is completed, and the excitation circuit 118 energizes the induction coil. Is switched to ON-OFF control, and the surface temperature of the heating roller 102 is maintained at the specified temperature.

  Next, the recording paper 106 onto which the image of the unfixed toner 107 has been transferred is conveyed to the fixing nip Y, where it is fused and fixed to the toner 108 image by the heat of the heating roller 102 and the pressure of the pressure roller 103. It is fixed on the top and becomes a robust image.

  FIG. 4 is a schematic cross-sectional view of a color image forming apparatus 150 that is an application example of the fixing apparatus 101. The color image forming apparatus 150 is a so-called tandem printer in which four color visible image forming units 140Y, 140M, 140C, and 140B are arranged along the conveyance path of the recording paper 106. Specifically, four sets of visible image forming units 140Y, 140M, 140C, and 140B are arranged along the conveyance path of the recording paper 106 that connects the supply tray 120 of the recording paper 106 and the fixing device 101, and recording is performed. Each color toner is multiplex-transferred onto the recording paper 106 conveyed by the conveying belt 133 of the paper conveying means 130, and then fixed by the fixing device 101 to form a full color image. The recording paper conveying means 130 has an endless conveying belt 133 that is stretched by a pair of driving rollers 131 and an idling roller 132 and that is rotated at a predetermined peripheral speed (134 mm / s in this embodiment). The recording paper 106 is electrostatically adsorbed onto the belt and conveyed. Each of the visible image forming units 140Y, 140M, 140C, and 140B is configured by arranging a charging roller 142, a laser beam irradiation unit 143, a developing device 144, a transfer roller 145, and a cleaner 146 around the photosensitive drum 141. In each unit, yellow (Y), magenta (M), cyan (C), and black (B) toners are respectively accommodated. Each of the visible image forming units 140Y, 140M, 140C, and 140B forms a toner image on the recording paper 106 by the following process.

  That is, after the surface of the photosensitive drum 141 is uniformly charged by the charging roller 142, the surface of the photosensitive drum 141 is laser-exposed according to image information by the laser light irradiation unit 143 to form an electrostatic latent image. Thereafter, a toner image is developed on the electrostatic latent image on the photosensitive drum 141 by the developing device 144, and the visualized toner image is recorded by the transfer roller 145 to which a bias voltage having a polarity opposite to that of the toner is applied. Transfer is sequentially performed on the recording paper 106 conveyed by the paper conveying means 130.

  Thereafter, the recording paper 106 is peeled off from the transport belt 133 by the curvature of the driving roller 131 and then transported to the fixing device 101. Therefore, as described above, an appropriate temperature and pressure are given by the heating roller 102 and the pressure roller 103 maintained at a specified temperature. The toner is dissolved and fixed to the recording paper 106, and a robust image is obtained.

  As described above, in the induction heating type fixing device 101 of the present invention, the heating roller 102 has a hollow shape, and the magnetic field generating member 104 is disposed so as to surround the heating roller 102. A heat storage member 105 is provided through the layer.

  Therefore, in order to efficiently heat by induction heating, even if the heat capacity of the heating roller 102 is reduced in consideration of the skin effect, the heat storage member 105 can suppress the heat radiation of the heating roller 102 and reduce the temperature drop. During heating, the heat generated by the heating roller 102 does not flow directly into the heat storage member 105, so that the rise time is hardly affected and the energy during heating is not increased. In this way, the heating roller 102 can be easily heated and difficult to cool, the start-up time at the time of reheating can be shortened, and the power required for the preheating operation during standby can be reduced. An energy heat fixing device can be realized.

  In addition, since the cross-sectional area of the heat insulating member 112 that supports the heat storage member 105 is formed to be different between the large-diameter plate-like portion 112a on the heat storage member 105 side and the small-diameter shaft portion 112b on the machine body side, The heat stored in the heat storage member 105 can be made difficult to escape to the outside.

  Japanese Patent No. 2616433 describes that the magnetic field generating means is disposed so as to surround the heating roller, but the inside of the heating roller remains hollow, and heating using the halogen lamp is performed. Although it is more efficient than the device, if the heat capacity of the heating roller is reduced to shorten the start-up time at start-up, the heat roller will be easy to cool, and it takes a long time to start up at the time of reheating, resulting in poor response. . On the other hand, when the heat capacity is increased, the responsiveness at the time of reheating is improved, but the start-up time at the start-up becomes longer.

FIG. 5 is a cross-sectional view in the axial direction of the heating roller 102 in the fixing device 151 according to the second reference embodiment, which serves as a reference for explaining the present invention. The fixing device 151 is similar to the fixing device 101 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that this fixing device 151 is provided with sealing (blocking) members 152 that restrict the inflow and outflow of air at the openings at both ends of the heating roller 102.

  Accordingly, the inside of the heating roller 102 is hermetically sealed, and the heat stored in the heat storage member 105 can be further prevented from escaping to the outside. The sealing member 152 is made of the same material as that of the heat insulating member 112 described above.

FIG. 6 is a cross-sectional view in the axial direction of the heating roller 102 in the fixing device 161 according to the third reference embodiment, which serves as a reference for explaining the present invention. The fixing device 161 is similar to the fixing device 101 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. In the fixing device 161, the heat storage member 105 is not provided in the heating roller 102, and a sealing member 152 that restricts the inflow and outflow of air is provided at the openings at both ends of the heating roller 102.

  As a result, the inside of the heating roller 102 is hermetically sealed and heat can be stored. Furthermore, since the heat storage member 105 is not provided inside the heating roller 102, there is no restriction in reducing the diameter of the heating roller 102. Therefore, the image forming apparatus can be reduced in size by configuring the fixing device 161 in this way. Also in this case, the sealing member 152 can use the same material as that of the heat insulating member 112 described above.

Note that the second reference embodiment and the third reference embodiment can also be applied to the color image forming apparatus 150 of FIG. 4 as in the first reference embodiment.

Induction heating apparatus, for example, and is applied as a fixing apparatus used in an electrophotographic image forming apparatus. FIG. 7 is a schematic cross-sectional view of a fixing device according to a fourth reference embodiment, which serves as a reference for explaining the present invention, and the basic configuration will be described using this.

As shown in FIG. 7, in the fixing device 301 of this preferred embodiment, using a cylindrical roller (heating roller) 302 to the heating member, contact with the pressure roller (pressure member) to the heating roller 302 303 and the heating An unfixed sheet on which an image has been formed on a recording sheet (heated material) 306 with a hot-melt resin such as toner is passed through a fixing nip Y formed by a roller 302, so that the recording sheet 306 is heated and pressed. It is configured to fix the image.

  An induction coil (magnetic field generating means) 304 for heating the heating roller 302 is disposed on the outer peripheral portion of the heating roller 302. A temperature detection element (thermistor) 351 for detecting the temperature of the heating roller 302 is in contact with the heating roller 302, and the induction coil 304 is controlled by the excitation circuit 352 based on the detection result.

  The induction coil 304 has a shape that covers the semicircular circumference of the heating roller 302, and a magnetic member 353 is disposed in a region opposite to the heating roller 302. The magnetic member 353 and the induction coil 304 are attached to an insulating holder 354 (see FIGS. 10 to 12).

The above is the most basic configuration of the fourth reference embodiment. Next, the fourth reference embodiment will be described in detail with reference to FIG.

  The heating roller 302 is configured to have at least one conductive layer 350 in order to generate heat upon receiving a varying magnetic field. The conductive layer 350 having a large relative permeability is suitable. For example, it is desirable to be composed of iron, magnetic stainless steel (SUS430, etc.), silicon steel plate, electromagnetic steel plate, nickel steel or the like. Even if the material has a low relative magnetic permeability, a material having a high resistivity (for example, nonmagnetic stainless steel: SUS304) may be used because it generates a large amount of heat when an eddy current is generated. Alternatively, it may be configured such that the material having a high relative permeability is disposed on a nonmagnetic base member (for example, ceramic) so as to have conductivity. In this embodiment, an iron roller (material: STKM) having a diameter of 30 mm and a thickness of 0.4 mm is used as the heating roller 302.

  The surface of the heating roller 302 is configured to have a release layer 309 in order to prevent toner from being offset (attached to the heating roller 302). For the release layer 309, fluorine-based materials such as PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and PTFE (polytetrafluoroethylene), silicone rubber, fluororubber, and the like are suitable. In this embodiment, 20 μm of PTFE is coated.

  Next, the induction coil 304 that is a magnetic field generating means will be described. The purpose of the induction coil 304 is to heat the heating roller 302 by eddy current. When the induction coil 304 is arranged outside the heating roller 302 as shown in FIG. 7, since the curvature exists, the magnetic flux concentrates on the center side of the induction coil 304, and the amount of eddy current generated increases. When the material of the heating roller 302 is made of a material having a high magnetic permeability, the magnetic flux is further concentrated, so that the heating efficiency is improved as described above.

Next, the shape of the induction coil 304 used in this reference embodiment is shown in FIG. 8 (three drawings: a plan view, a front view, and a side view). In this reference form, a single aluminum wire (with a surface insulating layer (for example, an oxide film)) is used in consideration of heat resistance, but it may be a copper wire or a copper-based composite member wire, or a litz wire (enamel) It may be a twisted wire). Whichever wire is used, in order to suppress the Joule loss in the coil, the total resistance value of the induction coil 304 should be 0.5Ω or less, preferably 0.1Ω or less. In addition, although only one induction coil 304 is shown in the longitudinal direction of the heating roller 302, a plurality of induction coils 304 may be arranged according to the size of the recording paper 306 to be fixed.

Next, the magnetic member 353 arranged along the induction coil 304 on the outer side of the induction coil 304 will be described. The magnetic member 353 is preferably made of a material having a higher magnetic permeability than the heating roller 302, and ferrite (nickel / manganese, manganese / ferrite, etc.), silicon steel plate, electromagnetic steel plate, and the like are suitable. If the magnetic member 353 is conductive, an eddy current is generated at that portion. Therefore, the magnetic member 353 is preferably formed by sintering or a laminated structure. In this preferred embodiment, using the ferrite sintered alloy of nickel-manganese-based.

Next, the arrangement structure of the magnetic member 353 will be described. As shown in FIG. 9, in this preferred embodiment, the magnetic member 353 is attached to the induction coil 304 via the heat resistant resin of the holder portion 354.

  Although the cross-sectional shape of the magnetic member 353 is constant in the longitudinal direction of the heating roller 302, the magnetic member 353 is influenced by the magnetic flux distribution interlinked with the heating roller 302. When the cross-sectional shape is changed in the longitudinal direction and the thickness of the magnetic member 353 is t1 and t2, the temperature distribution of the heating roller 302 may be controlled by setting t1 <t2 (FIG. 10). Further, as shown in FIG. 11, the circumferential length is changed (w1 <w2 where w1 and w2 are circumferential lengths), and the distance from the induction coil 304 is set to the heating roller 302. The same effect can be obtained even if the structure is changed in the longitudinal direction (FIG. 12). In each of the above drawings, the magnetic member 353 shows an example in which the cross-sectional shape is sharply changed, but the cross-sectional shape may be configured to change smoothly and continuously. In this case, the magnetic member 353 may be configured by another magnetic member 353 in a portion having a different shape, or a plurality of magnetic members 353 having different relative magnetic permeability may be disposed. Furthermore, the magnetic member 353 may be configured individually as illustrated in FIGS. 10 to 12 or may be configured in combination.

  By disposing the magnetic member 353 outside the induction coil 304 in this way, it is possible to realize the fixing device 301 that can easily control the temperature distribution regardless of how the induction coil 304 is wound. In addition, since the induction coil 304 has a curvature, the magnetic flux concentration effect on the heating roller 302 is large, so that the magnetic flux can be effectively concentrated with a small number of the magnetic members 353.

  The pressure roller 303 is configured to have a heat-resistant elastic body layer such as silicone rubber on an iron / stainless steel or aluminum cored bar. A release layer may be formed on the surface. The pressure roller 303 is pressed against the heating roller 302 with a force of 100 N by an elastic member (spring) not shown. As a result, a fixing nip Y having a width of about 3.5 mm is formed between the heating roller 302 and the heating roller 302.

  Next, a fixing operation in the fixing device of the present embodiment configured as described above will be described. First, at the time of warm-up, the excitation circuit 352 connected to the induction coil 304 is turned on, the induction coil 304 is excited, an AC eddy current is excited in the conductive layer 350 of the heating roller 302, and heat is generated by Joule heat. The amount of heat generated at this time is about 800 W. In addition, simultaneously with the start of energization by the excitation circuit 352, the pressure roller 303 is driven to rotate as the heating roller 302 is driven to rotate. The surface temperature of the heating roller 302 is constantly detected by the temperature detection element 351. When the surface temperature of the heating roller 302 reaches a predetermined temperature (180 ° C. in this embodiment), the warm-up is completed, and the induction coil by the excitation circuit 352 is completed. The energization to 304 is switched to ON-OFF control, and the surface temperature of the heating roller 302 is maintained at a predetermined temperature.

  Next, the recording paper (heated material) 306 onto which the unfixed toner image is transferred is conveyed to the fixing nip Y, and the toner image is melted and fixed by the heat of the heating roller 302 and the pressure of the pressure roller 303, and the recording paper The image is fixed on 306 and becomes a robust image.

  The induction heating device described above can be used not only as a fixing device but also as a heating device such as a drying device in a wet electrophotographic apparatus, a drying device in an inkjet printer, or an erasing device for rewritable media.

FIG. 13 shows a fifth reference embodiment which is a reference for explaining the present invention. As shown in the figure, the basic configuration is the same as the fourth reference embodiment, the fourth reference embodiment differs from the insulating member 355 is provided between the induction coil 304 and the heating roller 302 It is a point which becomes the structure which can isolate | separate both separately. A detailed view of the insulating member 355 and the induction coil 304 mounting portion is shown in FIG. 14 (the magnetic member 353 is omitted). The insulating member 355 is configured to cover the outer peripheral surface of the heating roller 302. As the material of the insulating member 355, a material having heat resistance such as PPS (polyphenyl sulfide), PI (polyimide), ceramic, or the like is suitable. The insulating member 355 includes a coil mounting rib 356 for holding the induction coil 304 and a holder portion 354. The induction coil 304 is sandwiched between the coil mounting rib 356 and the holder portion 354 so that the induction coil 304 is insulated. 355 is configured not to be in close contact with the entire surface. With such a configuration (the insulating member 355 and the induction coil 304 are formed of different members, or a part of the induction coil 304 is fixed to the insulating member 355), the linear expansion coefficient is obtained. Since the difference in thermal expansion between the two due to the difference between the two can be absorbed, peeling that occurs when the two are integrated can be prevented.

  Further, by reducing the contact area between the induction coil 304 and the insulating member 355, heat transmitted from the heating roller 302 to the induction coil 304 through the insulating member 355 can be reduced. That is, the ambient temperature of the induction coil 304 is lowered, and Joule loss that occurs as the temperature rises can be reduced.

FIG. 15 shows a first embodiment of the present invention . The basic structure is the same as the fourth reference embodiment, the fourth reference embodiment differs, the induction coil 304 is provided with the insulating member 355 between the heating roller 302, the insulating member 355 insulating This is because the layer 359, the heat insulating member 357, and the nonmagnetic member 358 having good heat conductivity are included.

  For the insulating layer 359, the above-described materials such as PPS, PI, and ceramic are used. The heat insulating member 357 is disposed to suppress the conductivity of heat transmitted from the heating roller 302. Suitable materials include heat-resistant silicone or urethane sponges (foams), non-woven fabrics made of heat-resistant fibers such as amides and aramids, and glass wool. In this embodiment, a silicon heat-resistant sponge is used. Further, in order to improve the heat resistance characteristics, the insulating member 355 itself may be constituted by a member having a porous structure, or may be constituted by a composite member containing glass fibers inside.

  In the present embodiment, it is more desirable to dispose a good heat conductive member 358 on the heating roller 302 side of the insulating member 355. With this configuration, nonuniformity due to the location of heat reaching the induction coil 304 from the heating roller 302 can be reduced, so that twisting or deflection due to heat distribution of the insulating member 355 can be prevented. . In addition, since the temperature distribution around the induction coil 304 becomes uniform, the life of the surface insulating layer formed on the surface of the induction coil 304 can be extended.

  The good heat conductive member 358 is preferably a good conductor having a low magnetic permeability, such as aluminum or copper, so as not to be affected by the varying magnetic field generated by the induction coil 304. In this embodiment, an aluminum thin film is used.

  Further, the good heat conductive member 358 may have at least one layer on either the heating roller 302 side or the induction coil 304 side of the heat insulating member 357, and is arranged so as to be led to the outside of the fixing device 371. May be. With this configuration, the heat flux reaching the induction coil 304 from the heating roller 302 is further suppressed, so that the temperature around the induction coil 304 is lowered and the life of the surface insulating layer of the induction coil 304 can be extended. .

  Further, in order to suppress heat radiation from the heating roller 302, the surface of the insulating member 355, the heat insulating member 357, or the good heat conductive member 358 may be surface-treated so as to have a low emissivity. As the surface treatment, there are methods such as forming a thin layer of aluminum or copper by vapor deposition or sputtering, applying a white heat-resistant paint, and improving surface properties (improving surface roughness).

  In the present embodiment, the case where the magnetic member 353 is provided outside the induction coil 304 is shown. However, the same effect can be obtained even when the present configuration is applied without the magnetic member 353. Can do.

Fourth reference embodiment of the fixing device 301, a fixing device 371 of the fixing device 361 and the first embodiment of the fifth reference embodiment is applicable to a color image forming apparatus 150 shown in FIG. The operation of the color image forming apparatus 150 is the same as that in the first reference embodiment, and a description thereof will be omitted.

The present invention can have a form having the following configuration .
(1) a conductive layer in which a current is induced in a varying magnetic field, and a heating member having a hollow structure;
A magnetic field generating means arranged to surround the heating member and for generating a variable magnetic field in the conductive layer;
A pressure member disposed opposite to the heating member, for conveying the sheet-like material to be heated between the heating member and the heating member;
An induction heating apparatus comprising: a heat storage member disposed in an internal space of the heating member via an air layer between the inner wall of the heating member.

In order to efficiently heat by induction heating, it is necessary to reduce the heat capacity of the heating roller (heating member) in consideration of the skin effect. For this reason, there is a drawback that it is easy to cool. Therefore, when storing heat in the heating roller, if the magnetic field generating means is disposed in the heating roller, the temperature of the coil also increases, which not only makes it difficult to coat the coil, but also increases Joule loss. The problem arises. When the resistance value of the coil is R and the current value flowing through the coil is I, Joule loss is represented by I ² R.

  For this reason, the heating roller has a hollow shape, the magnetic field generating means is arranged so as to surround the heating roller, a heat storage member is provided in the internal space of the vacant heating roller via an air layer, and the heating roller is It is easy to heat and hard to cool, suppresses heat dissipation after the end of heating, and reduces temperature drop. That is, since the heat storage member is arranged through the air layer, the heat of the heating roller does not flow directly into the heat storage member during heating, so that the rise time is hardly affected and the energy of the heating is not affected. Only the heat storage effect is exhibited without causing an increase.

  Thereby, at the time of reheating, it is possible to shorten the time for raising the heating roller to the specified temperature value together with the heat retaining effect of the heat storage member, and it is possible to reduce the power required for the preheating operation during standby. . Due to the above effects, for example, an energy-saving immediate heat fixing device can be realized.

  By disposing the heat storage member in the internal space of the heating roller (heating member), the heating roller can be easily heated and not easily cooled, heat dissipation after the heating is completed, and a temperature drop can be suppressed.

  (2) The induction heating device, wherein the cross-sectional area of the support member that supports the heat storage member changes as the heat storage member moves away from the heat storage member.

  Since the cross-sectional area of the support member is changed according to the distance from the heat storage member, the heat resistance of the support member changes in the middle, and the heat stored in the heat storage member can be made difficult to escape to the outside.

  (3) The said supporting member is comprised with the material which has heat insulation, The induction heating apparatus characterized by the above-mentioned.

  By configuring the support member with a member having low thermal conductivity, it is possible to make it difficult for the heat stored in the heat storage member to escape to the outside.

  (4) An induction heating apparatus characterized in that a sealing member for restricting the inflow and outflow of air is disposed in the opening of the heating member.

  By disposing the sealing member and suppressing the inflow and outflow of air, it is possible to make it difficult for the heat stored in the heat storage member to escape to the outside.

(5) a conductive layer in which a current is induced in a varying magnetic field, and a heating member having a hollow structure;
A magnetic field generating means arranged to surround the heating member and for generating a variable magnetic field in the conductive layer;
A pressure member disposed opposite to the heating member, for conveying the sheet-like material to be heated between the heating member and the heating member;
An induction heating apparatus comprising: a sealing member that is disposed in an opening of the heating member and restricts the inflow and outflow of air in the internal space.

  By suppressing the inflow and outflow of air, heat can be stored in the heating roller (heating member), and it can be made difficult to escape to the outside. In the configuration in which the heat storage member is arranged inside the heating roller, the heat storage member has a size. Therefore, the heating roller is limited in size. However, in this configuration, the heat storage member is not included. This is advantageous when reducing the roller diameter.

1 is a cross-sectional view in a direction perpendicular to an axis showing a structure of a fixing device which is an induction heating device according to a first reference embodiment serving as a reference for explaining the present invention; 2A is a cross-sectional view in the axial direction of the fixing device shown in FIG. 1, and FIG. 2B is a diagram showing a configuration in which a slit is provided in the heat insulating member. FIG. 3 is a perspective view showing a coil shape in the fixing device shown in FIGS. 1 and 2. 1 is a schematic cross-sectional view of a color image forming apparatus which is an application example of a fixing device. FIG. 6 is an axial cross-sectional view of a heating roller portion in a fixing device according to a second reference embodiment serving as a reference for explaining the present invention. FIG. 10 is a cross-sectional view in the axial direction of a heating roller portion in a fixing device according to a third reference embodiment which is a reference for explaining the present invention. It is a schematic block diagram (sectional drawing) of the induction heating apparatus which is the 4th reference form used as the reference for demonstrating this invention. FIG. 8A is a plan view showing a schematic configuration of a magnetic field generating means (induction coil) applied to the induction heating device of the present invention, FIG. 8B is a front view thereof, and FIG. It is the side view. In the induction heating apparatus of this invention, it is a figure which shows the state which attaches a magnetic member to a magnetic field generation means. It is a figure which shows the example of a form of the magnetic member in this invention. It is a figure which shows another example of a magnetic member in this invention. It is a figure which shows another example of a form of the magnetic member in this invention. It is the figure which showed the structural example of the induction heating apparatus which is the 5th reference form used as the reference for demonstrating this invention. It is a figure which shows the state which attaches a magnetic field generation means to an insulating member in the induction heating apparatus shown in FIG. It is the figure which showed the structural example of the induction heating apparatus which is 1st Embodiment of this invention. It is a figure which shows the example of 1 structure of the conventional induction heating apparatus.

Explanation of symbols

101, 151, 161, 301, 361, 371 Induction heating device (fixing device)
102,302 Heating roller (heating member)
103,303 pressure roller (pressure member)
104, 304 Magnetic field generating means (induction coil, magnetic field generating member)
105 Heat storage member 106,306 Recording paper (heated material)
109,350 Conductive layer 110,309 Release layer 111 Bearing 112,357 Thermal insulation member 152 Sealing member 118,352 Excitation circuit 353 Magnetic member 354 Holder part 355 Insulating member

Claims (3)

A heating member having a conductive layer in which a current is induced in a varying magnetic field;
A magnetic field generating means arranged to surround the heating member and for generating a variable magnetic field in the conductive layer;
An induction heating device that is disposed opposite to the heating member and includes a pressure member that presses the heated material against the heated member in order to transmit the heat of the heated member to the heated material,
A magnetic member is provided along the outer periphery of the magnetic field generating means,
Either the cross-sectional area of the magnetic member perpendicular to the longitudinal direction of the heating member, the length along the circumferential direction of the heating member, or the distance to the magnetic field generating means varies along the longitudinal direction of the heating member. and,
An insulating member disposed between the magnetic field generating means and the heating member, and formed separately from the magnetic field generating means;
An induction heating apparatus characterized in that a low-permeability good thermal conductive member is provided on at least one surface of the insulating member on the heating member side or the magnetic field generating means side . 2. The induction heating apparatus according to claim 1 , wherein the insulating member is made of a heat insulating material . An image forming apparatus comprising the induction heating device according to claim 1 .

Images